Coated abrasive products containing aggregates

ABSTRACT

A coated abrasive product includes a particulate material containing green, unfired abrasive aggregates having a generally spheroidal or toroidal shape, the aggregates formed from a composition comprising abrasive grit particles and a nanoparticle binder. Free abrasive products, bonded abrasive products, and the particulate material also contain aggregates.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority from U.S. Provisional PatentApplication No. 61/082,731, filed Jul. 22, 2008, entitled “CoatedAbrasive Products Containing Aggregates,” naming inventor Shelly C.Starling, James Manning, Colleen Rafferty, Mark Sternberg and AnthonyGaeta, which application is incorporated by reference herein in itsentirety.

BACKGROUND

1. Field of the Disclosure

The present disclosure is generally directed to abrasive particulatematerial, abrasive products incorporating abrasive particulate material,and methods for machining workpieces.

2. Description of the Related Art

Abrasive products are generally contain or formed from abrasiveparticulate material. Such abrasive particulate material can be used asa free abrasive, such as in the form of a slurry, or a fixed abrasive,typically either a coated abrasive or a bonded abrasive article.Abrasive products are used in various industries to machine workpieces,such as by lapping, grinding, or polishing. Machining utilizing abrasivearticles spans a wide industrial scope from optics industries,automotive paint repair industries, dental applications, to metalfabrication industries. Machining, such as by hand or with use ofcommonly available tools such as orbital polishers (both random andfixed axis), and belt and vibratory sanders, is also commonly done byconsumers in household applications. In each of these examples,abrasives are used to remove bulk material and/or affect surfacecharacteristics of products (e.g., planarity, surface roughness).

Surface characteristics include shine, texture, and uniformity. Forexample, manufacturers of metal components use abrasive articles to finepolish surfaces, and oftentimes desire a uniformly smooth surface.Similarly, optics manufacturers desire abrasive articles that producedefect free surfaces to prevent light diffraction and scattering. Hence,the abrasive surface of the abrasive article generally influencessurface quality.

Abrasive particle formation, such as through chemical synthesis routesor through bulk material processing routes (e.g., fusion andcomminution), is considered a fairly well developed and mature art area.Accordingly, notable developmental resources have been dedicated todevelopment of macrostructures, such as development of engineeredabrasives products within the context of coated abrasives and particularthree-dimensional structures and formulations in the context of bondedabrasives. Despite continued developments, a need continues to exist inthe art for improved particulate material.

Particulate materials include essentially single phase inorganicmaterials, such as alumina, silicon carbide, silica, ceria, and harder,high performance superabrasive grains such as cubic boron nitride anddiamond. Enhanced and even more sophisticated abrasive properties havebeen achieved through development of composite particulate materials.Such materials include formation of aggregates, which can be formedthrough slurry processing pathways that include removal of the liquidcarrier through volatilization or evaporation, leaving behind greenagglomerates, followed by high temperature treatment (i.e., firing) toform usable, fired agglomerates.

Such composite agglomerates have found commercial use in variousabrasive product deployments. However, the industry continues to demandeven further improved particulate materials, and particularly compositeaggregates that may offer enhanced machining performance.

SUMMARY

According to one embodiment, a coated abrasive product includes asubstrate and particulate material bonded thereto, the particulatematerial containing green, unfired abrasive aggregates having agenerally spheroidal or toroidal shape, the aggregates formed from acomposition comprising abrasive grit particles, a nanoparticle binder.

According to another embodiment, an abrasive slurry includes green,unfired abrasive aggregates provided in suspension, the aggregateshaving a generally spheroidal or toroidal shape, the aggregatescomprising an abrasive grit particles and a nanoparticle binder.

According to another embodiment, a fixed abrasive in the form of abonded abrasive includes green, unfired abrasive aggregates that arefixed in position with respect to each other with an inter-aggregatebinder, the aggregates having a generally spheroidal or toroidal shape,the aggregates comprising an abrasive grit particles and a nanoparticlebinder.

According to another embodiment, a method for forming abrasiveparticulate material includes forming a slurry comprising a liquidcarrier, abrasive grit particles and a nanoparticle binder; and spraydrying the slurry to form green, unfired aggregates containing theabrasive grit particles and the nanoparticle binder. Further, theaggregates are classified for use in an abrasive product

According to another embodiment, a method for machining a workpieceincludes providing a workpiece having an initial surface roughnessRa_(i), abrading the workpiece with a single abrasive product to removematerial from the workpiece, whereby the workpiece has a final surfaceroughness Ra_(f) and Ra_(f) is not greater than 0.2Ra_(i).

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIGS. 1-3 are photomicrographs taken with a scanning electron microscopeshowing abrasive aggregates including diamond grit combined with silicananoparticles in a coating on a substrate according to one embodiment ofthe present disclosure.

FIGS. 4-6 are photomicrographs taken with a scanning electron microscopeshowing abrasive aggregates including silicon carbide grit combined withsilica nanoparticles in a coating on a substrate according to anotherembodiment of the present disclosure.

FIG. 7 represents the results of Thermal Gravimetric Analysis (TGA) ofexamples according to embodiments.

FIG. 8 shows the consequence of post-synthesis heat treatment of diamondcontaining aggregate corresponding to an embodiment.

FIGS. 9-16 show various aggregates formed in accordance with differentformulations or processing parameters.

FIGS. 17 and 18 include magnified images of an abrasive product using aporous substrate material.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

According to an embodiment, abrasive aggregates are provided that areparticularly suitable for machining operations, in which abrasion iscarried out to remove material and improve surface quality. Abrasiveaggregates can be formed through slurry-based processing. Here,embodiments may take advantage of spray drying, where a slurrycontaining the constituent materials of the aggregates and a liquidcarrier, such as water, are mixed together, nebulized into droplets, anddried. In more detail, certain embodiments combine an abrasive grit,which may be in the form of microparticles, a binder, which may be inthe form of a nanoparticles, and a liquid carrier, which can be waterfor ease of handling and processing. Various embodiments further includea plasticizer, also known as a dispersant, in the slurry to promotedispersion of the abrasive grit within the thus formed, spray driedaggregates.

As used herein, the term “microparticle” may be used to refer to aparticle having an average particle size of from about 0.1 microns toabout 50 microns, preferably not less than 0.2 microns, 0.5 microns, or0.75 microns, and not greater than about 20 microns, such as not greaterthan 10 microns. Particular embodiments have an average particle sizefrom about 0.5 microns to about 10 microns.

As used herein, the term “nanoparticle” may be used to refer to aparticle having an average particle size of from about 5 nm to about 150nm, typically less than about 100 nm, 80 nm, 60 nm, 50 nm, or less thanabout 40 nm. Typical average particle sizes of nanoparticles lie withina range of about 20 nm to about 50 nm

As used herein, the term “aggregate” may be used to refer to a particlemade of a plurality of smaller particles that have been combined in sucha manner that it is relatively difficult to separate or disintegrate theaggregate particle into smaller particles by the application of pressureor agitation. This is in contrast to the term “agglomerate” used hereinto refer to a particle made of a plurality of smaller particles whichhave been combined in such a manner that it is relatively easy toseparate the aggregate particle or disintegrate the particle back intothe smaller particles, such as by the application of pressure or handagitation. According to present embodiments, the aggregates have acomposite structure, including both abrasive grits that have a sizewithin the microparticle range, and a nanoparticle binder that providesthe matrix of the aggregate in which the abrasive grits are embedded orcontained. As will be described in more detail, aggregates according toembodiments have notable morphology, characterized by uniformdistribution of the abrasive grits in the nanoparticle binder.

Of notable consequence, aggregates according to various embodiments arein the green, unfired state. Here, the aggregates are utilized as or inan abrasive product without notable post-formation heat treatment, suchas calcining, sintering, or recrystallization, that alter thecrystallite size, grain size, density, tensile strength, young'smodulus, and the like of the aggregates. Such heat treatment processesare commonly carried out in ceramic processing to provide usableproducts, but are not utilized herein. Such heat treatment steps aregenerally carried out in excess of 400° C., generally 500° C. and above.Indeed, temperatures can easily range from 800° C. to 1200° C. and abovefor certain ceramic species.

The abrasive grit particles generally have a Mohs hardness of greaterthan about 3, and preferably from about 3 to about 10. For particularapplications, the abrasive grit particles have a Mohs hardness not lessthan 5, 6, 7, 8, or 9. The abrasive grit particles are generallybelieved to serve as the primary active grinding or polishing agent inthe abrasive aggregates. Examples of suitable abrasive compositionsinclude non-metallic, inorganic solids such as carbides, oxides,nitrides and certain carbonaceous materials. Oxides include siliconoxide (such as quartz, cristobalite and glassy forms), cerium oxide,zirconium oxide, aluminum oxide. Carbides and nitrides include, but arenot limited to, silicon carbide, aluminum, boron nitride (includingcubic boron nitride), titanium carbide, titanium nitride, siliconnitride. Carbonaceous materials include diamond, which broadly includessynthetic diamond, diamond-like carbon, and related carbonaceousmaterials such as fullerite and aggregate diamond nanorods. Materialsmay also include a wide range of naturally occurring mined minerals,such as garnet, cristobalite, quartz, corundum, feldspar, by way ofexample. Certain embodiments of the present disclosure, take advantageof diamond, silicon carbide, aluminum oxide, and/or cerium oxidematerials, with diamond being shown to be notably effective. Inaddition, those of skill will appreciate that various other compositionspossessing the desired hardness characteristics may be used as abrasivegrit particles in the abrasive aggregates of the present disclosure. Inaddition, in certain embodiments according to the present disclosure,mixtures of two or more different abrasive grit particles can be used inthe same aggregates.

As should be understood from the foregoing description, a wide varietyof abrasive grit particles may be utilized in embodiments. Of theforegoing, cubic boron nitride and diamond are considered“superabrasive” particles, and have found widespread commercial use forspecialized machining operations, including highly critical polishingoperations. Further, the abrasive grit particles may be treated so as toform a metallurgical coating on the individual particles prior toincorporation into the aggregates. The superabrasive grits areparticularly suitable for coating. Typical metallurgical coatingsinclude nickel, titanium, copper, silver and alloys and mixturesthereof.

In general, the size of the abrasive grit particles lies in themicroparticle range. It should be noted that the abrasive grit particlescan be formed of abrasive aggregates of smaller particles such asabrasive aggregates nanoparticles, though more commonly the abrasivegrits are formed of single particles within the microparticle range. Forinstance, a plurality of nano-sized diamond particles may be aggregatedtogether to provide a microparticle of diamond grit. The size of theabrasive grit particles can vary depending upon the type of gritparticles being used. For example, in certain embodiments of the presentdisclosure, diamond grit particles are preferably used having a size ofabout 0.5 to 2 microns, such as about 1 micron. In other embodiments ofthe present disclosure, silicon carbide grit particles are preferablyused having a size of about 3 to about 8 microns. In still otherembodiments of the present disclosure, aluminum oxide grit particles arepreferably used having a size of about 3 to about 5 microns.

The abrasive grit particles may, in general, constitute between about0.1% to about 85% of the aggregates. The aggregates more preferablyinclude between about 10% to about 50% of the abrasive grit particles.

In one embodiment according to the present disclosure, abrasiveaggregates may be formed using a single size of abrasive grit particle,the size of the grit particle and the resultant aggregates both beingtailored to the desired polishing application. In another embodiments,mixtures of two or more differently sized abrasive grit particles may beused in combination to form abrasive aggregates having advantageouscharacteristics attributable to each of the grit particle sizes.

The abrasive aggregates according to the present disclosure also includea nanoparticle binder material as stated above. The nanoparticle bindergenerally forms a continuous matrix phase that functions to form andhold the abrasive grit particles together within the abrasive aggregatesin the nature of a binder. In this respect, it should be noted that thenanoparticle binder, while forming a continuous matrix phase, is itselfgenerally made up of individually identifiable nanoparticles that are inintimate contact, interlocked and, to a certain extent, atomicallybonded with each other. However, due to the green, unfired state of thethus formed aggregates, the individual nanoparticles are generally notfused together to form grains, as in the case of a sintered ceramicmaterial. As used herein, description of nanoparticle binder extends toone or multiple species of binders.

While the grit material is believed to act as the primary abrasive, thenanoparticle material can also act as a secondary abrasive in someembodiments of the aggregates of the present disclosure. The size andpolishing characteristics of the aggregates may be adjusted by varyingparameters such as the composition of the nanoparticle binder material,the relative concentration ratio of nanoparticle binder material toabrasive grit particle, and the size of the abrasive grit particles. Thenanoparticle binder material may itself comprise very fine ceramic andcarbonaceous particles such as nano-sized silicon dioxide in a liquidcolloid or suspension (known as colloidal silica). Nanoparticle bindermaterials may also include, but are not limited to, colloidal alumina,nano-sized cerium oxide, nano-sized diamond, and mixtures thereof.Colloidal silica is preferred for use as the nanoparticle binder incertain embodiments of the present disclosure. For example, commerciallyavailable nanoparticle binders that have been used successfully includethe colloidal silica solutions BINDZEL 2040 BINDZIL 2040 (available fromEka Chemicals Inc. of Marietta, Ga.) and NEXSIL 20 (available fromNyacol Nano Technologies, Inc. of Ashland, Mass.).

Before the mixture is spray dried to form the aggregates, the mixturemay include an amount of nanoparticle binder material ranging betweenabout 0.1% to about 80%, preferably ranging between about 10% to about30% on a wet basis. In the formed abrasive aggregates, the nanoparticlebinder material may constitute between about 1% to about 90% of theaggregates, preferably between about 20% to about 80% of the aggregates,and most preferably between about 50% to about 75% of the aggregates,all on a dry weight basis.

The slurry for forming the abrasive aggregates also can advantageouslyinclude another material which serves primarily as a plasticizer, alsoknown as a dispersant, to promote dispersion of the abrasive grit withinthe thus formed aggregates. Due to the low processing temperatures used,the plasticizer is believed to remain in the thus formed aggregates, andhas been quantified as remaining by thermal gravimetric analysis (TGA).The plasticizer might also assist in holding together the grit particlesand nanoparticle binder material in an aggregate when the mixture isspray dried.

In this respect, FIG. 7 shows the results of TGA analysis on both SiCcontaining aggregates and diamond containing aggregates, showingresidual plasticizer removal from 250° C. to about 400° C. Of note, thediamond was found to burn out at high temperatures. It bears noting thatthe TGA analysis was done purely as a characterization tool, and theelevated temperatures to which the aggregates were exposed was not partof the process flow for forming aggregates.

Plasticizers include both organic and inorganic materials, includingsurfactants and other surface tension modifying species. Particularembodiments make use of organic species, such as polymers and monomers.In an exemplary embodiment, the plasticizer is a polyol. For example,the polyol may be a monomeric polyol or may be a polymeric polyol. Anexemplary monomeric polyol includes 1,2-propanediol; 1,4-propanediol;ethylene glycol; glycerin; pentaerythritol; sugar alcohols such asmalitol, sorbitol, isomalt, or any combination thereof, or anycombination thereof. An exemplary polymeric polyol includes polyethyleneglycol; polypropylene glycol; poly(tetramethylene ether)glycol;polyethylene oxide; polypropylene oxide; a reaction product of glycerinand propylene oxide, ethylene oxide, or a combination thereof, areaction product of a diol and a dicarboxylic acid or its derivative; anatural oil polyol; or any combination thereof. In an example, thepolyol may be a polyester polyol, such as a reaction products of a dioland a dicarboxylic acid or its derivative. In another example, thepolyol is a polyether polyol, such as polyethylene glycol, polypropyleneglycol, polyethylene oxide, polypropylene oxide, or a reaction productof glycerin and propylene oxide or ethylene oxide. In particular, theplasticizer includes polyethylene glycol (PEG).

The plasticizer, notably polyethylene glycols, can have a range ofmolecular weights. Suitable molecular weights lie within a range ofabout 10 to 3000, such as 50 to 1000, 50 to 500, or 50 to 400. PEG 200has been found to be a particularly useful plasticizers according tocertain embodiments of the present disclosure. Plasticizerconcentrations in the mixture, before spray drying, may range betweenabout 0.5% to about 40%, and preferably between about 0.5% to about 5%.

As should be clear, the composition used for forming the aggregatescontains major species of abrasive grit, nanoparticle binder, andoftentimes a plasticizer. These species may be present in variousrelative contents in the composition for forming the aggregates. Therelative solids content in the aggregates should mirror the solidscontent in the composition for forming the aggregates, though the finalcontent of the plasticizer may be altered due to drying/volatilizationduring the spray drying process, though TGA analysis as showsplasticizer retention in the aggregates. The composition may includeabout 0.1 to about 85 weight percent of the abrasive grit particles,from about 0.1 to about 80 weight percent of the nanoparticle binder,and from about 0.5 to about 40 weight percent of the plasticizer, weightpercents based on the total solids content of the composition. Incertain embodiments, the composition can contain about 10 to 50 weightpercent abrasive grit particles, about 50 to 90 weight percentnanoparticle binder, and about 0.5 to 15 weight percent plasticizer.Particular embodiments s about 15 to 40 weight percent abrasive gritparticles and about 60 to 85 weight percent nanoparticle binder.

A volatile liquid is also included in the composition, which acts as acarrier and serves to liquefy or fluidize the mixture of the abrasivegrit particles, the nanoparticle binder material, and the plasticizer,so that the mixture may be flowed into a spray dryer, nebulized intofine aggregate droplets, and dried therein. Preferably, the volatileliquid carrier is deionized water, although other volatile liquids maybe used that will be driven off by typical spray drying temperatures anddo not substantially alter the composition of the mixture. The liquefiedmixture may include the abrasive grit particles, the nanoparticle bindermaterial, and a plasticizer, the balance being a volatile liquid. Thecomposition, in the form of a slurry, can be water-based and can includebetween about 7.5% to about 15% abrasive grit particles, between about2.5% to about 7.5%, and between about 0.5% to about 1.5% plasticizer,percents based on total weight of the slurry.

During processing, it should be noted that in certain embodimentsaccording to the present disclosure, it is preferred to substantiallyremove any accumulated static charges from the grit particles prior totheir addition to the mixture. It has been observed that the stabilityof the aggregates formed in the spray drying step is substantiallyimproved if the grit particles are substantially free of accumulatedCoulombic charges. Once well mixed, the liquefied mixture, including thecomponents of the abrasive grit particle, the nanoparticle bindermaterial, and the plasticizer, is then processed in a spray dryer inorder to form the abrasive aggregates.

Various spray drying apparatuses may be used, including a rotaryatomizer, a single fluid nozzle atomizer, and a two-fluid nozzleatomizer. For mixtures having relatively smaller abrasive gritparticles, and for forming relatively smaller aggregates, the spraydryer is preferably a rotary atomizer. For mixtures having relativelylarger abrasive grit particles, particularly those larger than about 80microns, and for forming relatively larger aggregates, particularlythose larger than about 90 microns, a single fluid or two-fluid nozzleatomizer may be preferred.

The spray dryer apparatus will typically include at least two materialcollection points, one at the cyclone and one at the bottom of the maindrying chamber. Aggregates formed according to the present disclosurecan be collected from both locations; however, the aggregates collectedfrom cyclone have been observed generally be smaller in size and lighterin weight while the aggregates collected from the main drying chamberhave been observed to generally be larger in size and heavier in weight.Aggregates collected from the cyclone of the dryer have been observed totypically have a size of from about 5 to about 25 microns. On the otherhand, aggregates collected from the main drying chamber have beenobserved to typically have a size of from about 20 to about 100 microns.

To commence spray drying, the slurry is pumped into the spray dryapparatus at a generally constant rate. The slurry then passes throughan atomizer or nebulizer inside the spray dryer to form generallyspheroidal droplets. While passing through the atomizer, these dropletsare caught up in a vortex of hot air, in which the liquid portion of theslurry essentially instantly evaporates and the solid portion of theslurry forms an aggregate. The hot air that volatilizes the liquidfraction of the slurry, leaving behind solid particles, is typically notgreater than 400° C., such as not greater than 375° C., 350° C., or 300°C. Typically, spray drying is carried out at a temperature greater thanabout 80° C., such as greater than about 90° C. Particular embodimentshave been carried out at temperatures of about 90° C. to about 250° C.It is noted that dwell times within the high temperature portion of thespray dryer are generally limited to seconds, such as 0.5 to 10 seconds,which is in stark contrast to typically heat treatment dwell timesassociated with sintering, calcination, or firing of typical ceramicproducts.

When the slurry enters the vortex of hot air the liquid is substantiallydriven off and the mixture is formed into a fine powder includingnumerous aggregates, each abrasive aggregate being generally spheroidalin shape. As used here in the term “spheroidal” refers to aggregateshaving a spherical shape, or a generally spherical shape, includingellipsoids and other spherical permutations, which are a consequentresult of the spray drying process. Thus, spheroids include spheres,ellipsoids, truncated spheres and ellipsoids, but all generally have arounded rather than blocky structure. As should be clear, the aggregateseach contain the abrasive grit particles bound together by thenanoparticle binder material and any residue of the plasticizer that hasnot been evaporated. The final moisture content of the aggregates, thespray drying step, is generally from about 1 to about 3 percent byweight.

Advantageously, according the present disclosure, no further processingsteps that notably modify the composition or morphology of theas-formed, unfired, green spray dried aggregates are required in orderto produce usable abrasive aggregates. In fact, according to certainembodiments of the present disclosure, the method for making theaggregates consists essentially of only the aforementioned mixing andspray drying steps, and quite notably, heat treatment steps that wouldaffect the morphology of the aggregates are avoided. In particular, nostep is carried in which the materials are heated to extremely hightemperatures in the range of from about 500° C. to 1000° C. or more inorder to melt, sinter, or otherwise fuse the silica or othernanoparticle binder in the mixtures. Thus, in certain embodimentsaccording to the present disclosure, all of the steps of the method ofmaking the aggregates may be carried at temperatures of about 400° C. orless.

This stands in contrast to conventional processes for making abrasivepowders with aggregated particles which typically require a sinteringstep at very high temperatures of from about 500° C. to 1000° C. ormore.

Although the aggregates are not believed to require a sintering or othersimilar high temperature treatment, the formed aggregates have beenfound to be highly durable. In particular, it has been observed that,once formed, the aggregates are resistant to dissolution in a widevariety of chemical solvents including methyl ethyl ketone (MEK),isopropyl alcohol (IPA), and 1,4-dioxane.

Once formed, the aggregates may be classified, or separated into varioussize ranges as desired before being applied to a substrate or otherwiseutilized in a polishing operation. In addition to the abrasiveaggregates, the resultant powder may include an amount of materialsmaller than the desired grain size. The particulate material composedof the thus formed aggregates generally has an average particle sizewithin a range of about 10 to 150 microns. Typically, the material hasan average particle size not less than about 20, such as not less thanabout 25 microns. Upper limits for average particle size are driven byprocess constraints and particular end use applications, and generallythe material has an average particle size not greater than about 100microns, such as not greater than about 90, 80, or even not greater than70 microns. In certain embodiments, the average particle size of theaggregate material is preferably between about 20 microns and 50microns. The size, and the size range, of the aggregates may be adjustedand may depend on many factors, including the composition of the mixtureand the spray dryer feed rate. For example, abrasive aggregates of sizesincluding those of approximately 10 microns. 20 microns, 35 microns, 40microns, and 45 microns have been successfully produced using a rotaryatomizing spray dryer. These aggregates have included abrasive gritparticles ranging from about 5 to about 8 microns.

When viewed under magnification, the aggregates have a generallyspheroidal shape, being characterized as rounded or spherical as seen inthe scanning electron micrographs of FIGS. 4-6. In some instances,however, the aggregates may be observed to have an void near the centerof the aggregate and thus exhibit a more toroid-or torus-like shape asseen in the scanning electron micrographs of FIGS. 1-3. Individualparticles of the abrasive grit material, such a diamond grit, may beobserved to be dispersed over the surface of the aggregates and withinthe interior thereof, with relatively few instance of the individualgrit particles clumping together on the surface of the aggregate. It isnoted that FIGS. 1-6 show dispersed, individual aggregates that arebound together in a resin binder system.

Further study of the abrasive aggregates has revealed that certainembodiments are composed of hollow spheroids. Such particles can beanalogized to thick-shelled racquet balls, having a wall thickness t_(w)within a range of about 0.08 to 0.4 times the average particle size ofthe aggregates. Process parameters and compositional parameters can bemodified to effect different wall thicknesses, such as wall thicknessesnot less than about 0.1, 0.15 times the average particle size of theaggregates. Upper limits for wall thickness may be on the order of 0.35,0.30, 0.25, or 0.20 times the average particles size of the aggregates.

Additional studies show that specific surface areas (SSA)are generallygreater than 2 m²/g, such as greater than 10 m²/g, greater than 10 m²/g,or greater than 15 m²/g. Maximum SSA has been observed to be not greaterthan 150 m²/g, such as not greater than 100 m²/g.

Once formed, the abrasive aggregates can be used ‘as-is’ with suitableclassification to refine particle size distribution. Whilepost-synthesis process steps such as excessive heat treatment areavoided, such that the aggregates are used in a green, unfired state,the aggregates can be coated with a metallurgical coating, in much thesame fashion that individual abrasive grits can be coated. Metallurgicalcoatings nickel, titanium, copper, silver and alloys and mixturesthereof.

Once produced, the abrasive aggregates may be used directly as a looseor ‘free’ abrasive powder. In this context, the abrasive powder formedfrom the aggregates may be used as either a dry powder or a powder whichhas been wetted with a liquid such as water to create a slurry forimproved performance. The abrasive powder may also be incorporated intoa polishing paste or gel. The abrasive powder so produced mayadvantageously be used for the finishing and/or polishing of numerousother materials such as chemical mechanical planarization (CMP) used inthe semiconductor industry, fine surface finishing of various materials,and polishing both natural and artificial dental materials.Alternatively, the aggregates are configured into a fixed abrasive, aterm that broadly includes coated and bonded abrasive products.

In other embodiments of the present disclosure, however, the abrasiveaggregates are preferably combined with a resin material used to adherethe aggregates onto a surface of a substrate. Processes for combiningthe aggregates with the resin bonding material include slurry formation,in which the aggregates, resin and other additives are combined togetherand coated on a substrate, or in a distinct processing pathway,aggregates are placed on a resin coated substrate through electrostaticattraction or simply through gravity (e.g., sprinkled on the substrate).The latter approach is well understood in the art, generally firstdepositing a ‘make coat’ on the substrate, aggregate application on themake coat, and subsequent deposition of a ‘size coat.’ Optionally, asupersize coat may be deposited over the size coat. Further, a compliantcoat may be disposed between the make coat and the substrate. In anotherexample, a back coat may be disposed over the substrate on a sideopposite the make coat.

In connection with slurry coating a substrate, in addition to theaggregates, the slurry generally also includes a solvent such as wateror an organic solvent and a polymeric resin material. Suitable polymericresin materials include polyesters, epoxy resins, polyurethanes,polyamides, polyacrylates, polymethacrylates, poly vinyl chlorides,polyethylene, polysiloxane, silicones, cellulose acetates,nitrocellulose, natural rubber, starch, shellac, and mixtures thereof.Most preferably, the resin is a polyester resin. The slurry mayadditionally comprise other ingredients to form a binder system designedto bond the aggregate grains onto a substrate. The slurry composition isthoroughly mixing using, for example, a high shear mixer.

The slurry containing the aggregate grains is preferably applied to thesubstrate using a blade spreader to form a coating. Alternatively, theslurry coating may be applied using slot die, gravure, or reversegravure coating methods. The coating thickness may range from about 1 toabout 5 mils in thickness, after drying. As the substrate is fed underthe blade spreader at a desired coat speed, the aggregate grain slurryis applied to the substrate in the desired thickness. The coat speed ispreferably between about 10 to about 40 feet per minute.

The coated substrate is then heated in order to cure the resin and bondthe aggregate grains to the substrate. In general, the coated substrateis heated to a temperature of between about 100° C. to less than about250° C. during this curing process. In certain embodiments of thepresent disclosure, it is preferred that the curing step be carried at atemperature of less than about 200° C.

Once the resin is cured and the aggregate abrasive grains are bonded tothe substrate, and the coated substrate may be used for a variety ofstock removal, finishing, and polishing applications.

In an alternative embodiment of the present disclosure, the abrasiveaggregates may be directly incorporated into the substrate. Forinstance, the aggregates may be mixed a polyester resin and this mixtureof aggregates and polymer may then be formed into a substrate.

In a still alternative embodiment of the present disclosure, theabrasive aggregates may be applied to a substrate coated with anadhesive and then sealed. This coating technique is similar thattypically used for traditional sandpaper, and is referenced above. Inthis embodiment, the abrasive aggregates are preferably not mixed into aslurry. Instead the abrasive powder containing the aggregates ispreferably fed onto a substrate to which an adhesive has already beenapplied, the make coat, followed by sealing via the size coat.Optionally, the substrate may be pre-treated with a compliant coat or aback coat.

In an alternative embodiment of the present disclosure, the abrasiveaggregates could be applied to substrates or other materials byelectroplating, electric-static, spray coating and spray powder coatingmethods.

The abrasive-coated substrate may them be used as a lapping film or amicro-finishing film for finishing and /or polishing other materials.Substrate materials which may be coated in this manner include, but arenot limited to, polyester, polyurethane, polypropylene, polyimides suchas KAPTON from DuPont, non-woven materials, woven materials, paper, andmetals including foils of copper, aluminum, and steel. Polyester filmsare particularly preferred as the substrate material is certainembodiments of the present disclosure. Suitable substrates may have athickness, before being coated, of from about 1 to about 14 mils.

In certain embodiments, the abrasive product may utilize a highly poroussubstrate material, such as a foam material. Porous substratesfacilitate swarf removal during abrasive applications and may also proveuseful in applications where a pliable material is suitable. The amountof porosity is typically on the order of at least about 40 vol %, andaccording to certain embodiments, at least about 50 vol %, 60 vol %, 70vol %, 80 vol % or even at least about 90 vol %. Particular embodimentshave a porosity within a range between about 50 vol % and 90 vol %.

Generally, the porosity in such substrates can be open, closed, or acombination thereof. Still, particular embodiments utilize poroussubstrate materials having a majority of open porosity. That is, theporosity is an interconnected network of pores extending through thephysical, lattice structure of the substrate. A certain amount of openporosity may be desirable since the interconnected network of poresallows additives, coats, and particulate material to penetrate into theinterior of the substrate material, which may be suitable for theformation of certain abrasive products.

In the context of porous substrates, some suitable materials can includeorganic materials. For example, synthesized organic materials such aspolyolefins, and more particularly polymers including polystyrene,polyester, polyurethane, polypropylene, polyethylene,polymethacrylimide, polyamide, polylactic acid, polyacrylate,polysulphone, polyacetate, fluorinated polymers, and chlorinatedpolymers.

The formation of abrasive products using porous substrates can becompleted in accordance with embodiments described herein. For example,the forming process can include any number of coats, such as a makecoat, size coat, supersize coat, or even a back coat. In particular,binders or adhesives to which the particulate material is bonded to thesubstrate can include a spray coating application to assure penetrationof the pores. Additionally, the particulate material may be appliedusing a similar process ensuring that a suitable amount particulatematerial is bonded to the substrate.

In some applications, a certain coating of particulate material on theavailable surface area of the lattice structure is desirable. Forexample, according to one embodiment, at least about 50% of theavailable surface area of the lattice structure is covered by theparticulate material. In accordance with other embodiments, theparticulate material covers a greater percentage of the availablesurface area of the lattice structure, such at least about 60%, 75%, 85%or even 95%. Certain embodiments utilize a coverage of particulatematerial on the available surface area within a range between about 50%and 100% and more particularly, between about 85% and 100%. FIGS. 17 and18 provide magnified images of portions of a highly porous substrateincluding particulate materials bonded to the lattice structure of thesubstrate.

Abrasive products utilizing a porous substrate may be useful in generalabrading operations including polishing and grinding applications oralternatively in cleaning applications. Such products may be used in avariety of industries, including for example, commercial, automotive,household, personal use, and medical industries. In fact, in comparativetests, the present abrasive product has outperformed state of the artabrasive cleaning products. For example, one such state-of-the-artproduct is the Mr. Clean Magic Eraser® available from Proctor andGamble.

Referring again more generally to the coated abrasive productsindependent of the type of substrate material, that is porous ornon-porous, other additives may be provided in the abrasive product.Additives can be added to any of the previously mentioned coats such asthe make coat, size coat, supersize coat, or back coat to give theabrasive product certain characteristics which may be suitable forcertain applications. Such additives can include anti-loading agents,abrasive fillers, plasticizers, anti-static agents, lubricants, wettingagents, grinding aids, pigments, dyes, coupling agents, release agents,suspending agents, curing agents, aromatic materials, and antimicrobialagents.

Anti-loading agents aid swarf removal during grinding and polishingapplications. Some such suitable anti-loading agents can includemetal-containing or organic-containing materials, or a combinationthereof. Particularly suitable organic-containing anti-loading agentscan include polymers having organyl groups including at least 4 carbonatoms, and more particularly at least 8 carbon atoms, for example,quaternary ammonium salt compounds having from about 15 to 35 carbonatoms. Other suitable organic anti-loading agents can include acids, forexample, saturated fatty acids having from about 4 to 22 carbon atoms.In some certain instances, partial esters may also be particularlysuitable.

Additionally, particularly suitable metal-containing materials caninclude metal stearates, metal palmitates, a combination thereof, andthe like. Certain other anti-loading agents can include salts, such asamine salts, lithium salts, combinations thereof and the like.Phosphoric-containing compounds, such as phosphoric acids, may also besuitable for use as anti-loading agents.

The abrasive products herein can include anti-loading agents havingsoftening points greater than about 50° C. Other anti-loading agents mayhave higher softening points depending upon the intended application,such as at least about 60° C., 75° C., 90° C., and more particularly,within a range between about 50° C. and 100° C. The anti-loading agentcan be applied to the abrasive product within one of the forming coats,such as the make coat, size coat, supersize coat, or back coat, but itwill be appreciated that such an additive can be applied in a differentmanner. For example, the anti-loading agent can be applied directly tothe substrate, in a separate application, such that it bonded to thesubstrate. In other embodiments, the anti-loading agent can be bonded tothe particulate material, for example, it may be contained within theparticulate material, such as bonded to the nanoparticle binder, oralternatively, within the hollow or interior space of the particulatematerial.

In the context of a supersize coat containing an anti-loading agent,generally the anti-loading agent is present in an amount between about50 wt % and 100 wt % of the total weight of the supersize coat. In thecontext of an anti-loading agent bonded to the substrate or containedwithin the particulate material, the amount of anti-loading agent may bethe same, or in some certain instances, it can be present in minoramounts.

In certain embodiments, it may be suitable to incorporate ananti-loading agent prior to the final formation of the particulatematerial. That is, the anti-loading agent can be provided during theformation of the particulate material. According to one particularembodiment, the anti-loading agent is provided in a binder orplasticizer used to form the particles, such as prior to a spray dryingprocess.

In further reference to particular additives, the abrasive product caninclude an anti-static agent that reduces the tendency of the abrasiveproduct to accumulate static electricity during a grinding or polishingapplication. Suitable anti-static agents can include hygroscopicmaterials. For example, the anti-static agent can include an organicmaterial, such as amines, carboxyls, and hydroxyls, a combinationthereof, and the like. Additionally, an anti-static agent can include ametal, and more particularly, oxides of metals, such as vanadium oxide.Other embodiments may use an anti-static agent including carbon.Carbon-containing anti-static agents can include graphite or carbonblack, which is typically formed by partial combustion of hydrocarbons.

Application of the anti-static agent to the abrasive product can be in amanner similar to that as described with respect to the anti-loadingagent. That is, it may be included within a coat overlying and bonded tothe substrate and or particulate material, such as the make coat, sizecoat, supersize coat, or even the back coat. Alternatively, theanti-static agent may be contained within a backing material attached toa surface of a substrate. In still another embodiment, the anti-staticagent can be bonded to the particulate material, that is, it may becontained within and bonded to the nanoparticle binder material, orcontained within an interior space of the hollow particulate material.In the particular context of providing an anti-static agent that isbonded to the particulate material, it may be suitable to provide suchan agent while forming the particulate material. For example, theanti-static agent can be added as part of a binder or plasticizermaterial used to form the particles.

Incorporation of an anti-static agent within the abrasive product canresult in a low surface resistivity product. In accordance with oneembodiment, the surface resistivity of the abrasive product includingthe anti-static agent is not greater than about 1E8 ohm/square. Otherembodiments may have lower surface resistivities, such as on the orderof not greater than about 1E7 ohm/square, 1E6 ohm/square, or even notgreater than about 1E5 ohm/square. Certain embodiments utilize anabrasive product having a surface resistivity within a range betweenabout 1E4 ohm/square and about 1E8 ohm/square.

In particular reference to other additives, the substrate can include anaromatic material such that an aroma or scent is released upon use ofthe abrasive product. Generally, reference to aromatic materials isreference to materials capable of releasing a fragrance, often apleasing fragrance, such as those associated with floral, musk, orcitrus smelling agents. The aromatic material can include notes akin toperfumes, such that it may include a base note, top note, or middlenote, and any combination thereof. Additionally, certain aromaticmaterials can include essential oils such as those found naturally andassociated with certain fragrances, or alternatively, syntheticmaterials developed to mimic naturally occurring fragrances of essentialoils. In accordance with a particular embodiment, the aromatic materialis an organic material, and can include compounds such as alcohols,aldehydes, amines, esters, ethers, ketones, lactones, terpenes, andthiols.

Provision of an aromatic material within the abrasive product allows forthe release of a pleasant fragrance upon use of the abrasive product.Accordingly, the provision of such aromatic materials within theabrasive product may be suitable for use in household or personalapplications where pleasant fragrances are associated with a level ofcleanliness. Like the other additives discussed herein, the aromaticmaterial can be applied to the abrasive product within a coat, such asthe size coat, make coat, supersize coat, or even the back coat. Inaccordance with a particular embodiment, the aromatic material is bondedto the substrate, and more particularly, may be contained within a coatoverlying a portion of the substrate and particulate material. Inaccordance with an alternative embodiment, the aromatic material iscontained within the particulate material, such that it can be containedand bonded to the nanoparticle binder, or alternatively contained withinan interior space of the hollow particulate material. In the particularcontext of an aromatic material that is bonded to the particulatematerial, it may be suitable to provide such a material during theformation of the particulate material. For example, the anti-staticagent can be added as part of a binder or plasticizer material used toform the particles.

In accordance with another particular embodiment, the abrasive productmay include an antimicrobial agent useful in commercial, industrial, andhousehold products, which is released upon the worksurface during theuse of the abrasive product thereby sterilizing the work surface.Suitable antimicrobial agents can include sterilants, sanitizers,disinfectants, and fungicides. More particularly, suitable antimicrobialagents typically include materials such as alcohol, phenolics, peroxide,ammonium-containing compounds, iodine-containing compounds, andchlorine-containing compounds. It will be appreciated that anantimicrobial agent can include one or a combination of any of the abovementioned chemical compounds, including more common examples such aschlorhexadine, trichlosan, bleach, and quaternary ammonium chloride.

Provision of antimicrobial agents within the abrasive product can bedone in such a manner that they are provided in one of various coatsused to form the final product, including the make coat, size coat,supersize coat, or back coat. In accordance with a particularembodiment, the antimicrobial agent may be bonded to the substrate, andmore particularly, overlying a portion of the substrate and bonded tothe particulate material such that upon conducting an abrasive processthe antimicrobial agent is released at the worksurface. In accordancewith a particular embodiment, the antimicrobial agent can be bonded tothe particulate material, such that it is contained within thenanoparticle binder, or alternatively contained within an interior spaceof the hollow particulate materials. In certain instances, where anantimicrobial agent is bonded to the particulate material, the agent maybe provided within a plasticizer or binder during the formation of theparticulate material.

Further, the abrasive aggregates may also be incorporated into bondedabrasives, such as diamond grinding wheels and other grinding wheels.Bonded abrasives may also used to provide high traction, non-slipmaterials which may be applied, for example, to ladder rungs. Here,typically bonded abrasives are three dimensional structures rather thanthe generally planar structure of a coated abrasive, and includes a 3dimensional matrix of bonding material in which the aggregates areembedded. That is, the bond material fixes position of the aggregateswith respect to each other, and is present as an inter-agglomeratephase. While bonded abrasives utilize a wide variety of bonding agents,such as resin, glass, and metals, certain agents such as glass and metalbond materials require high temperature processing. Accordingly, topreserve the green structure of the aggregates, generally resin systemsare used that do not require high cure temperatures, or which can becured with actinic radiation such as UV.

In one embodiment according to the present disclosure, the abrasiveproduct may be used for finishing and polishing telecommunicationscables, particularly fiber optic cables. Fiber optic cables are capableof transmitting vast amounts of data at very high speed in the form oflight pulses. To allow these light pulses to be effectively transmittedbetween interconnected fiber optic cables or between a fiber optic cableand a connected electronic device, however, the ends of the fiber opticconnectors must be cleanly cut or cleaved and then highly polished toproduce an extremely smooth surface and appropriate tip geometry.Abrasive substrate film produced according to the present disclosure andgenerally cut into disk or sheet form may be used for this purpose andhave been observed to be highly effective for the polishing of the endsof fiber optic connectors.

When used for polishing fiber optic connectors, the abrasive substratefilms are preferably produced from aggregates formed from diamond gritcombined with silica nanoparticle binder. The grit particles preferablyhave a size of about 1 micron, and the overall size of the aggregates ispreferably from about 30 to about 80 microns. These aggregates arepreferably bonded to a polyester film substrate. Polishing of the fiberoptic connector ends may be carried out on a fiber optic polishingmachine. A suitable 12 connector polishing machine is available fromDomaille Engineering of Rochester, Minn. and may be used with theabrasive substrate films of the present disclosure for polishing fiberoptic connectors at, for example, a speed of about 60 rpm and with anapplied pressure of about 8 psi.

In another embodiment according to the present disclosure, the abrasiveproduct may be used for stock removal, finishing and polishing hardmetal surfaces such as steel. When used for polishing metal surfaces,the abrasive substrate films are preferably produced from aggregatesformed from diamond grit combined with a silica nanoparticle binder. Thegrit particles preferably have a size of about 1 micron, and the overallsize of the aggregates is preferably from about 30 to about 80 microns.These aggregates are preferably bonded to polyester film substrate.Using this abrasive product, polishing of the surfaces may be carriedout, for example, using a Struers metal polishing machine (availablefrom Struers, Inc. of Westlake, Ohio) operating at a speed of 600 rpmand with an applied force of 15 newtons. Alternatively, hard metalsurfaces may also be polished using abrasive aggregates formed fromsilicon carbide grit combined with silica.

In another embodiment according to the present disclosure, the abrasiveproduct may be used for stock removal, finishing and polishing softermetal surfaces such as copper or brass. When used for polishing metalsurfaces, the abrasive substrate films are preferably produced fromaggregates formed from diamond grit combined with a silica nanoparticlebinder. The grit particles preferably have a size of about 3 to 5microns, and the overall size of the aggregates is preferably from about30 to about 80 microns. These aggregates are preferably bonded topolyester film substrate. Using this abrasive product, polishing of thesurfaces may be carried out, for example, using a Struers metalpolishing machine (available from Struers, Inc. of Westlake, Ohio)operating at a speed of 150 rpm and with an applied force of 45 newtons.Alternatively, soft metal surfaces may also be polished using abrasiveaggregates formed from silicon carbide grit combined with silica.

In still another embodiment according to the present disclosure, theabrasive substrate may be used for finishing and polishing coatedsurfaces, such as painted surfaces. In particular, the abrasivesubstrate film may be used to buff or polished painted automotivesurfaces. When used for polishing painted automotive surfaces, theabrasive substrate films are preferably produced from aggregates formedfrom silicon carbide grit embedded within a silica nanoparticle binder.The grit particles preferably have a size of from about 3 to about 8microns, and the overall size of the aggregates is preferably from about30 to about 50 microns. These aggregates are preferably bonded to apolyester film substrate.

In the context of coated surfaces, it has been observed that theabrasive products herein are useful for changing the appearance ofpainted surfaces. In particular, it is noted that the abrasive productsare suitable for reducing the surface roughness of painted surfaces, andthereby increasing the gloss of a painted surface. Upon abrading apainted surface having a dull or semi-glossy paint with the abrasiveproduct, the surface roughness is reduced such that the gloss of thetreated surface is increased to a final gloss, G_(f) that is greaterthan an initial gloss, G_(i). Such measured changes in glossiness appearmore prevalently at certain angles, such as at 60° or 85°. In accordancewith an embodiment, the change in gloss is a notable change such thatthe final gloss G_(f) is at least two times greater than the initialgloss G_(i) as measured by a gloss meter BYK Micro Trigloss Meter 4430according to ASTM standard test D2457. In other embodiments, the changebetween the initial gloss and the final gloss is greater, such that thefinal gloss G_(f) is at least 4 times the initial gloss G_(f), and moreparticularly within a range between about 2 times to about 4 times ofthe initial gloss G_(i) measured at angle of about 60°.

At greater angles, the change in the gloss between the final gloss G_(f)and initial gloss G_(i) may be greater. In accordance with oneembodiment, the final gloss G_(f) measured at an angle of 85° is atleast about 3 times the initial gloss G_(i), and more particularlywithin a range between about 2 times and 6 times the initial gloss G_(i)measurement.

Other embodiments can particularly include finishing in dentalapplications. Here, an abrasive product such as a coated abrasive,containing green, unfired aggregates as described herein can be utilizedquite successfully for finishing tooth and dental prosthetics.

Typically the polishing of materials such as those described above iscarried out in a multi-step, incremental process. The surface is firstpolished with a relatively coarse abrasive material and then polishedagain with a somewhat finer grit abrasive material. This process may berepeated several times, which each successive re-polishing being carriedout with a progressively finer grit abrasive until the surface ispolished to the desired degree of smoothness. This type of multi-steppolishing procedure has conventionally been required as typically thegrains of an abrasive must be on the same scale as the size of thescratches which they are to remove. Certain polishing protocols usesuccessively finer products having a grit size, and attendant Ra (withrespect to both the abrasive product and on the workpiece post-machiningstep) reduced by a factor of three. That is, successively finer productsare generally limited to reduction by a factor of three (e.g., from 9micron, to 6 micron, to 3 micron grit sizes), in order to ensure defectremoval from the preceding machining step.

In contrast to the conventional multi-step procedure, however, it hasbeen quite surprisingly and unexpectedly observed that a wide variety ofworkpieces, from materials such as fiber optic connectors, metalssurfaces, and painted automotive surfaces, and dental prosthetics, maybe polished in a single step process using single, rather than multipleabrasive product, such as a coated abrasive product according to thepresent disclosure. This result is quite surprising and highlyadvantageous. It is been observed that when abrasive substratesaccording to the present disclosure are used, the entire polishing maybe carried out using only one abrasive. This results in a considerablereduction in the time needed to achieve a desired degree of polishingsmoothness, as well as marked reduction in costs.

Without being bound by theory, it is believed that the advantage may bederived from the unique properties observed in the aggregates of thepresent disclosure. The average roughness, or R_(a,) of a surface is ameasure of the degree of variations in the overall height profile of asurface. A lower roughness value is generally indicative of a surfacewhich is smoother and has smaller variations in overall height betweendiffering locations on the surface. When the roughness value of abrasivematerials is measured, the roughness values observed can typically becorrelated to the average size of the abrasive particles. For example,with conventional diamond grit abrasives, the size of the diamond gritand the expected roughness values for the abrasives are typically asfollows:

Diamond grit size Typical roughness value (microns) (R_(a)) (microns) 302.5 15 1.6 9 1.0 6 0.8 3 0.6 1 0.3

To finish or polish a surface to a desired final maximum roughness (i.e.to a desired final minimum degree of smoothness), conventionally anabrasive must be employed having a corresponding maximum degree ofroughness.

The aggregates of the present disclosure, however, have been observedhave a roughness value in excess of what would typically be expected fora grit particle having a comparable size. Thus, while a typical 30micron diamond grit particle would generally have a roughness values ofabout 2.5 microns (as noted above), 30 micron aggregates formed from 1micron diamond grit and a silica nanoparticle binder according to thepresent disclosure have been observed to have a roughness value of fromabout 5 to about 6 microns.

Even more surprisingly, despite this high roughness value, it has beenobserved that these same aggregates according to the present disclosuremay be used for the fine polishing of surfaces. A finished surfacesmoothness corresponding to a roughness value of well below 1 micron maybe achieved using the aforementioned diamond grit and silica aggregateswhich, again, have been measured to roughness values of from about 5 toabout 6 microns. Conventionally, a grit particle having a size of about1 micron or less would be required to polish a surface to this degree ofsmoothness.

More concretely, based upon testing of numerous embodiments, it has beenfound that initial surface roughness of a work piece can be machined andpolished in a single step, utilizing a single abrasive product, wellbeyond the capability of a conventional single abrasive product. Forexample, for a workpiece having an initial surface roughness Ra_(i),embodiments herein have shown the capability of reducing the initialsurface roughness Ra_(i) to a final surface roughness as a result ofabrading the workpiece, the final surface roughness Ra_(f) being notgreater than 0.2 Ra_(i), such as not greater than 0.1 Ra_(i). Theforegoing achievement in the reduction of surface roughness by utilizinga single product bears notable attention, as state of the art abrasiveproducts are generally quite limited in surface roughness reductionutilizing a single product. Indeed, surface roughness reductions havebeen measured to values not greater than 0.5 Ra_(i), and even notgreater than about 0.01 Ra_(i), representing a notable 2 order ofmagnitude reduction in surface roughness Ra.

While it is not completely understood as to the precise reasons whyembodiments herein have demonstrated such machining efficacy, oftentimesspanning more than one order of magnitude reduction in Ra on a workpiece, it is theorized that the present green, unfired aggregates havingnotable composite structure is responsible for machining throughcomplementary simultaneous pathways. For example, it is believed thatthe aggregate size is responsible for large defect reduction (e.g.,removal of 6 to 7 micron scratches in a work piece). Meanwhile, theprimary abrasive grit is believed to be responsible for simultaneousreduction in medium sized defects, driving the Ra value of the workpieceeven further downward. And moreover, it is believed that thenanoparticle binder contributes to ultra-fine polishing of theworkpiece, driving Ra values of the workpiece down into the nanometerregime, such as on the order of 10 to 20 nanometers, observed forcertain work pieces.

It is emphasized that the green, unfired state of the aggregatescontributes to the notable machining efficacy described above. Bymaintaining the aggregates in the green, unfired state, it is understoodthat the nanoparticle binder, while composed of particles interlockedand to some extent atomically bonded together, nevertheless retains thedesirable ultra-fine polishing properties of the nanoparticle particles,which properties would be destroyed through higher temperature heattreatment. That is, the multi-action nature of the aggregates ismaintained through controlled process conditions, notably preventing theaggregates from being exposed to high temperatures over any sort ofnotable duration. Here, it is noted that it is likely not justtemperature alone, but also dwell time which would be responsible forhigh temperature aggregate degradation. For example, during spraydrying, droplets containing the solids fraction forming the aggregatesare typically exposed to elevated temperatures, such as up to about 400°C., for a mere few seconds, while conventional high temperature ceramicprocesses such as sintering, calcination or the like generally utilizedwell times on the order of 15 minutes to multiple hours. Accordingly,it is feasible that the aggregates according to the present embodimentsmay maintain their green state even upon exposure to elevatedtemperatures, provided that such elevation is restricted to the order ofseconds. Such would be the case to the extent that higher temperaturesfor spray drying processes were utilized.

It is also noted, that based on comparative testing, incorporation of aplasticizer in the slurry composition can be highly result effective.More specifically, in testing of diamond/colloidal silica containingaggregates, removal of plasticizer had a notable, negative impact. Theplasticizer helps maintain dispersion of the abrasive grits insuspension or slurry form, and stabilizes the suspension duringprocessing. Upon spray drying, it was observed that the abrasive gritsremain very well distributed. When the plasticizer is removed from theslurry composition, the resultant aggregates at first appeared notdifferent, and had requisite green strength for handling. However, upondeployment into an abrasive product, machining results were poor, withobserved aggregate failure. Without wishing to be bound by anyparticular theory, it is believed that the plasticizer enable theformation of a more structurally sound aggregate, by maintaining gritdispersion in the slurry and uniform distribution in the aggregate. Incontrast, comparative examples absent plasticizer had localized clumpsof grits, forming a weak area of the aggregate, subject to failure uponapplication of working pressures.

The uniform distribution of aggregates can easily be seen in FIG. 8,which is an example that was exposed to TGA described above, showingdiamond grit burnout due to high temperature volatilization. The voidareas shown in FIG. 8 illustrate diamond grit positions. It is alsonoted that the material left behind, heat treated nanoparticle binder,clearly forms a self supporting, continuous matrix. Of course, in thehigh temperature form shown in FIG. 8, the particulate nature of thebinder has been lost due to grain growth and sintering.

A further advantage may be found in the surprising durability ofabrasives made from the aggregates of the present disclosure. Abrasivestypically wear down and gradually lose their effectiveness in removingstock material from a surface being polished or finished with theabrasive. Abrasives incorporating the aggregates of the presentdisclosure, however, have been observed to have significantly improveddurability as compared to conventional abrasives materials. When used incomparable applications, abrasives incorporating the aggregates of thepresent disclosure have been observed to retain their effectiveness formore than twice as long as conventional abrasive materials, and in someinstances, up to 20 times as long.

The properties and advantage of the present disclosure are illustratedin further detail in the following nonlimiting examples. Unlessotherwise indicated, temperatures are expressed in degrees Celsius, andconcentrations are expressed in weight percentages based upon theoverall dry weight of the abrasive aggregates.

Example 1

A powder of fine abrasive aggregates including diamond grit combinedwith silica nanoparticles was produced by the following method. Anaqueous colloidal silica was mixed with diamond grit having an averageparticle size of 1.1 microns, along with a polyethylene glycol (PEG) 200plasticizer and deionized water. The silica sol used was BINDZIL 2040,available from Eka Chemicals Inc. of Marietta, Ga., which is believed tobe aqueous colloidal silica solution was used having about 40% silica(Si0₂) by weight, a silica particle size of about 20 nm, and abase-stabilized pH of about 10. The components were mixed in thefollowing amounts:

Component Pounds in mixture Diamond grit 6.6 BINDZIL 2040 silica sol13.2 PEG 200 0.9 Deionized water 45

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 20% solids in water.

The mixture was then spray dried using a Niro SD6.3 rotary atomizerspray dryer with an FF-1 atomizer available from Niro, Inc. of Columbia,Md. The mixture was heated and fed into the inlet of the spray dryer ata temperature of about 342° C. The outlet temperature of the spray dryerwas measured to be about 152° C. The spray drying process substantiallyremoved the water from the mixture and the remaining components wereobserved to form a powder of small, generally round aggregates whichwere collected for analysis. About 85% of the aggregate particles werecollected from the dryer cyclone unit and about 15% were collected fromthe main drying of the spray dryer apparatus. No further sintering orheating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the diamond grit. The average size of the aggregatescollected from the cyclone was measured to be about 20 microns. Theaverage size of the aggregates collected from the main drying chamberwas about 40 microns.

Example 2

A powder of fine abrasive aggregates including diamond grit combinedwith silica nanoparticles was produced by the following method. Anaqueous colloidal silica solution (BINDZIL 2040) was mixed with diamondgrit having an average particle size of 1.0 microns, along with apolyethylene glycol (PEG) 200 plasticizer and deionized water. Thecomponents were mixed in the following amounts:

Component Pounds in mixture Diamond grit 15.75 BINDZIL 2040 silica sol40 PEG 200 2.2 Deionized water 52.5

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 52% solids in water.

The mixture was then spray dried using the same Niro brand spray dryer.The mixture was heated and fed into the inlet of the spray dryer at atemperature of about 342° C. The outlet temperature of the spray dryerwas measured to be about 170° C. The spray drying process substantiallyremoved the water from the mixture and the remaining components wereobserved to form a powder of small, generally round aggregates. Theaggregates produced were collected for analysis with about 50% of theparticles being collected from the dryer cyclone unit and about 50%being collected from the main drying of the spray dryer apparatus. Nofurther sintering or heating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the diamond grit. The typical size of the aggregates wasmeasured to be about 35 to about 45 microns.

Example 3

A powder of fine abrasive aggregates including diamond grit combinedwith silica nanoparticles was produced by the following method. Anaqueous colloidal silica solution (BINDZIL 2040) was mixed with siliconcarbide grit (NGC 2500, available from Nanko Abrasives, Inc. of Tokyo,Japan) having an average particle size of 8 microns, along with apolyethylene glycol (PEG) 200 plasticizer and deionized water. Thecomponents were mixed in the following amounts:

Component Pounds in mixture Silicon carbide grit 75 BINDZIL 2040 silicasol 190 PEG 200 10.5 Deionized water 25

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 60% solids in water.

The mixture was then spray dried using the same Niro brand spray dryer.The mixture was heated and fed into the inlet of the spray dryer at atemperature of about 342° C. The outlet temperature of the spray dryerwas measured to be about 132° C. The spray drying process substantiallyremoved the water from the mixture and the remaining components wereobserved to form a powder of small, generally round aggregates. About150 pounds of the aggregates were collected with about 50% of theparticles being collected from the dryer cyclone unit and about 50%being collected from the main drying of the spray dryer apparatus. Nofurther sintering or heating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the silicon carbide grit. The average size of theaggregates was measured to be about 40 microns.

Example 4

In this example, a powder of silicon carbide and silica aggregatesproduced as described in Example 3 above, was coated and bonded to asubstrate. In order to apply the aggregate powder to the substrate, acoating slurry was first prepared including the aggregate powder, apolyester resin (VITEL 3301 available from Bostik, Inc. of Wauwatos,Wis.), a crosslinking agent, and methyl ethyl ketone solvent (availablefrom Quaker City Chemicals, Inc. of Philadelphia, Pa.) in the followingamounts:

Component Pounds in mixture Silicon carbide aggregates 81.6 Polyesterresin 50 Crosslinking agent 24.9 MEK solvent 75

The composition was mixed in order to provide a substantially uniformslurry mixer.

A roll of MYLAR Type A polyester brand film (available from DuPont) wasused as the substrate. The film had a thickness of 3 mils. A coating ofthe slurry was applied to the upper surface of the substrate film usinga blade coating system. The film was advanced through the blade coatingstation at a rate of 40 feet per minute and the slurry was coated ontothe substrate film at an initial thickness of about 3 mils.

As the coated substrate exited the blade coater, the film was advancedthrough an extended heating unit. The length of the heating sectionwithin the unit was about 37 feet and this heating section wasmaintained at a temperature of about 340° C. The coated will wasadvanced in the heating unit at a speed of 40 feet per minute. As thecoated film passed through the heating unit, the resin in the slurryunderwent a crosslinking (i.e. curing) reaction. Upon exiting theheating unit, this reaction was substantially complete and theaggregates were substantially bonded to the substrate film by thecrosslinked resin.

The finished, aggregate-bonded substrate film was then allowed to cooland thereafter was cut into a plurality of abrasive discs. The surfaceprofile of an abrasive disc sample was then analyzed using a Mahrprofilometer instrument from Mahr Federal Inc. of Providence, R.I. inorder to determine the roughness value (R_(a)) of the abrasive disc. Theroughness value was measured to be 5.85 microns.

Example 5

In this example, a lapping film substrate was coated with a combinationof two aggregate powders. The first was a powder made from diamond gritand silica aggregates as described in Example 1 above. The second was apowder made from silicon carbide and silica aggregates produced asdescribed in Example 3 above. In order to apply the aggregate powder tothe substrate, a coating slurry was first prepared including the twoaggregate powders, a polyester resin (available from Bostik, Inc. ofWauwatos, Wis.), a crosslinking agent, and methyl ethyl ketone solvent(available from Quaker City Chemicals, Inc. of Philadelphia, Pa.) in thefollowing amounts:

Component Pounds in mixture Silicon carbide aggregates 15.21 Diamondaggregates 35.3 Polyester resin 60 Crosslinking agent 0.6 MEK solvent 45

The composition was mixed in order to provide a substantially uniformslurry mixer.

A roll of MYLAR Type A polyester brand film was used as the substrate.The film had a thickness of about 3 mils. A coating of the slurry wasapplied to the upper surface of the substrate film using a blade coatingsystem. The film was advanced through the blade coating station at arate of 25 feet per minute and the slurry was coated onto the substratefilm at an initial thickness of about 2.5 mils.

As the coated substrate exited the blade coater, the film was advancedthrough an extended heating unit. The length of the heating sectionwithin the unit was about 37 feet and this heating section wasmaintained at a temperature of about 340° C. The coated will wasadvanced in the heating unit at a speed of 25 feet per minute for atotal heating time of about two minutes. As the coated film passedthrough the heating unit, the resin in the slurry underwent acrosslinking (i.e. curing) reaction. Upon exiting the heating unit, thisreaction was substantially complete and the aggregates weresubstantially bonded to the substrate film by the crosslinked resin.

The finished, aggregate-bonded substrate film was then allowed to cooland thereafter was cut into a plurality of abrasive discs. The surfaceprofile of an abrasive disc sample was then analyzed using a Mahrprofilometer instrument in order to determine the roughness value(R_(a)) of the abrasive disc. The roughness value was measured to be11.13 microns.

Example 6

A powder of fine abrasive aggregates including aluminum oxide grit heldwithin silica was produced by the following method. An aqueous colloidalsilica was mixed with aluminum oxide grit having an average particlesize of 3.27 microns, along with a polyethylene glycol (PEG) 200plasticizer and deionized water. The silica sol used was BINDZIL 2040,available from Eka Chemicals Inc. of Marietta, Ga., which is believed tobe aqueous colloidal silica solution was used having about 40% silica(Si0₂) by weight, a silica particle size of about 20 nm, and abase-stabilized pH of about 10. The components were mixed in thefollowing amounts:

Component Pounds in mixture Alum. Oxide grit 24 BINDZIL 2040 silica sol62 PEG 200 3.8 Deionized water 210

The components were thoroughly mixed using a high shear mixer for 15minutes to provide a uniform aqueous dispersion.

The mixture was then spray dried using the same Niro brand spray dryer.The mixture was heated and fed into the inlet of the spray dryer at atemperature of about 240° C. The outlet temperature of the spray dryerwas measured to be about 120° C. The spray drying process substantiallyremoved the water from the mixture and the remaining components wereobserved to form a powder of small, generally round aggregates. About 15pounds of the aggregates were collected from the cyclone section duringa 1.5 hour run of the spray dryer apparatus. No further sintering orheating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica and PEG with particles of the aluminum oxidegrit imbedded thereon. The average size of the aggregates was measuredusing a Microtrack size distribution analysis, using both wet and drysample methods. The average size was measured to be 17.08 microns by thewet sample method and 19.12 microns by the dry sample method. The finalmoisture content of the aggregates, after spray drying, was 1.4 weightpercent.

Example 7

A powder of fine abrasive aggregates including aluminum oxide grit heldwithin silica was produced by the following method. An aqueous colloidalsilica solution (BINDZIL 2040) was mixed with an aluminum oxide grithaving an average particle size of 3.27 microns, along with apolyethylene glycol (PEG) 200 plasticizer and deionized water. Thecomponents were mixed in the following amounts:

Component Pounds in mixture Alum. Oxide grit 24 BINDZIL 2040 silica sol62 PEG 200 3.8 Deionized water 210

The components were thoroughly mixed using a high shear mixer for 15minutes to provide a uniform aqueous dispersion.

The mixture was then spray dried using the same Niro brand spray dryer.The mixture was heated and fed into the inlet of the spray dryer at atemperature of about 343° C. The outlet temperature of the spray dryerwas measured to be about 150° C. The spray dryer was operated at 350Hertz. The spray drying process substantially removed the water from themixture and the remaining components were observed to form a powder ofsmall, generally round aggregates. A total of about 26 pounds of theaggregates were collected during a 2 hour run of the spray dryerapparatus, with about 8 pounds of aggregates being collected from themain drying chamber and about 18 pounds of aggregates being collectedfrom the cyclone. No further sintering or heating was required to formthe aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica and PEG with particles of the aluminum oxidegrit imbedded thereon. The average size of the aggregates was measuredusing a Microtrack size distribution analysis, using both wet and drysample methods. For the cyclone aggregates, the average size wasmeasured to be 20.38 microns by the wet sample method and 22.4 micronsby the dry sample method. For the drying chamber aggregates, the averagesize was measured to be 45.97 microns by the wet sample method and 45.91microns by the dry sample method. The final moisture content of theaggregates, after spray drying, was 1.76 weight percent for the cycloneaggregates and 1.54 for the drying chamber aggregates.

Example 8 Diamond 1 Chamber

A powder of fine abrasive aggregates including diamond grit combinedwith silica nanoparticles was produced by the following method. Anaqueous colloidal silica was mixed with diamond grit having an averageparticle size of 1.1 microns, along with a polyethylene glycol (PEG) 200plasticizer and deionized water. The silica sol used was BINDZIL 2040,available from Eka Chemicals Inc. of Marietta, Ga., which is believed tobe aqueous colloidal silica solution was used having about 40% silica(Si0₂) by weight, a silica particle size of about 20 nm, and abase-stabilized pH of about 10. The components were mixed in thefollowing amounts:

Component Pounds in mixture Diamond grit 6.6 BINDZIL 2040 silica sol13.2 PEG 200 0.9 Deionized water 45

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 20% solids in water.

The mixture was then spray dried using a Niro SD6.3 rotary atomizerspray dryer with an FF-1 atomizer available from Niro, Inc. of Columbia,Md. The mixture was heated and fed into the inlet of the spray dryer ata temperature of about 342° C. The outlet temperature of the spray dryerwas measured to be about 152° C. The spray drying process substantiallyremoved the water from the mixture and the remaining components wereobserved to form a powder of small, generally round aggregates whichwere collected for analysis. About 85% of the aggregate particles werecollected from the dryer cyclone unit and about 15% were collected fromthe main drying of the spray dryer apparatus. No further sintering orheating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the diamond grit. The average size of the aggregatescollected from the chamber was measured to be about 40-50 microns,SSA=72 m²/g. The aggregates are shown in FIG. 9.

Example 9 Diamond 1 Cyclone

A powder of fine abrasive aggregates including diamond grit combinedwith silica nanoparticles was produced by the following method. Anaqueous colloidal silica was mixed with diamond grit having an averageparticle size of 1.1 microns, along with a polyethylene glycol (PEG) 200plasticizer and deionized water. The silica sol used was BINDZIL 2040,available from Eka Chemicals Inc. of Marietta, Ga., which is believed tobe aqueous colloidal silica solution was used having about 40% silica(Si0₂) by weight, a silica particle size of about 20 nm, and abase-stabilized pH of about 10.

The components were mixed in the following amounts:

Component Pounds in mixture Diamond grit 6.6 BINDZIL 2040 silica sol13.2 PEG 200 0.9 Deionized water 45

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 20% solids in water.

The mixture was then spray dried using a Niro SD6.3 rotary atomizerspray dryer with an FF-1 atomizer available from Niro, Inc. of Columbia,Md. The mixture was heated and fed into the inlet of the spray dryer ata temperature of about 342° C. The outlet temperature of the spray dryerwas measured to be about 152° C. The spray drying process substantiallyremoved the water from the mixture and the remaining components wereobserved to form a powder of small, generally round aggregates whichwere collected for analysis. About 85% of the aggregate particles werecollected from the dryer cyclone unit and about 15% were collected fromthe main drying of the spray dryer apparatus. No further sintering orheating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the diamond grit. The average size of the aggregatescollected from the cyclone was measured to be about 25 microns, SSA=71m2/g. The aggregates are shown in FIG. 10.

Example 10 NGC 2500 Chamber

A powder of fine abrasive aggregates including NGC 2500 combined withsilica nanoparticles was produced by the following method. An aqueouscolloidal silica was mixed with NGC 2500 grit having an average particlesize of 8 microns, along with a polyethylene glycol (PEG) 200plasticizer and deionized water. The silica sol used was BINDZIL 2040,available from Eka Chemicals Inc. of Marietta, Ga., which is believed tobe aqueous colloidal silica solution was used having about 40% silica(Si0₂) by weight, a silica particle size of about 20 nm, and abase-stabilized pH of about 10. The components were mixed in thefollowing amounts:

Component Pounds in mixture NGC 2500 75 BINDZIL 2040 silica sol 190 PEG200 10.5 Deionized water 25

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 54% solids in water.

The mixture was then spray dried using a Niro SD6.3 rotary atomizerspray dryer with an FF-1 atomizer available from Niro, Inc. of Columbia,Md. The mixture was heated and fed into the inlet of the spray dryer ata temperature of about 342° C. The outlet temperature of the spray dryerwas measured to be about 152° C. The spray drying process substantiallyremoved the water from the mixture and the remaining components wereobserved to form a powder of small, generally round aggregates whichwere collected for analysis. About 50% of the aggregate particles werecollected from the dryer cyclone unit and about 50% were collected fromthe main drying of the spray dryer apparatus. No further sintering orheating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the NGC grit. The average size of the aggregates collectedfrom the chamber was measured to be about 40-50 microns, SSA 63 m2/g.The aggregates are shown in FIG. 11.

Example 11 CBN 9 Micron Chamber

A powder of fine abrasive aggregates including CBN combined with silicananoparticles was produced by the following method. An aqueous colloidalsilica was mixed with CBN grit having an average particle size of 9microns, along with a polyethylene glycol (PEG) 200 plasticizer anddeionized water. The silica sol used was BINDZIL 2040, available fromEka Chemicals Inc. of Marietta, Ga., which is believed to be aqueouscolloidal silica solution was used having about 40% silica (Si0₂) byweight, a silica particle size of about 20 nm, and a base-stabilized pHof about 10. The components were mixed in the following amounts:

Component Grams in mixture CBN 9 micron 204.3 BINDZIL 2040 silica sol454 PEG 200 27.24 Deionized water 72.64

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 54% solids in water.

The mixture was then spray dried using a Pentronix Model 370 rotaryatomizer spray dryer. The mixture was fed at room temperature into theinlet of the spray dryer at a temperature of about 220° C. The outlettemperature of the spray dryer was measured to be about 98° C. The spraydrying process substantially removed the water from the mixture and theremaining components were observed to form a powder of small, generallyround aggregates which were collected for analysis. About 5% of theaggregate particles were collected from the dryer cyclone unit and about95% were collected from the main drying of the spray dryer apparatus. Nofurther sintering or heating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the CBN grit. The average size of the aggregates collectedfrom the chamber was measured to be about 80 microns, SSA=62 m2/g. Theaggregates are shown in FIG. 12

Example 12 Nickel Coated CBN 15 Micron Chamber

A powder of fine abrasive aggregates including CBN combined with silicananoparticles was produced by the following method. An aqueous colloidalsilica was mixed with Nickel coated CBN grit having an average particlesize of 15 microns, along with a polyethylene glycol (PEG) 200plasticizer and deionized water. The silica sol used was BINDZIL 2040,available from Eka Chemicals Inc. of Marietta, Ga., which is believed tobe aqueous colloidal silica solution was used having about 40% silica(Si0₂) by weight, a silica particle size of about 20 nm, and abase-stabilized pH of about 10. The components were mixed in thefollowing amounts:

Component Grams in mixture Nickel coated CBN 15 micron 1200 BINDZIL 2040silica sol 454 PEG 200 29 Deionized water 63

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 81% solids in water.

The mixture was then spray dried using a Pentronix Model 370 rotaryatomizer spray dryer. The mixture was fed at room temperature into theinlet of the spray dryer at a temperature of about 220° C. The outlettemperature of the spray dryer was measured to be about 98° C. The spraydrying process substantially removed the water from the mixture and theremaining components were observed to form a powder of small, generallyround aggregates which were collected for analysis. About 5% of theaggregate particles were collected from the dryer cyclone unit and about95% were collected from the main drying of the spray dryer apparatus. Nofurther sintering or heating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of silica nanoparticles and PEG combined withparticles of the CBN grit. The average size of the aggregates collectedfrom the chamber was measured to be about 70 microns, SSA 23 m2/g. Theaggregates are shown in FIG. 13.

Example 13 NG C 2500

A powder of fine abrasive aggregates including NGC 2500 combined withCeria nanoparticles was produced by the following method. An aqueousNano Ceria was mixed with NGC 2500 grit having an average particle sizeof 8 microns, along with a polyethylene glycol (PEG) 200 plasticizer anddeionized water. The Nano Ceria used was by Degussa AG, AdvancedNanomaterials, which is believed to be aqueous Ceria solution was usedhaving about 40% Ceria) by weight, a silica particle size of about 38nm, and a base-stabilized pH of about 10. The components were mixed inthe following amounts:

Component Grams in mixture NGC 2500 168 Nano Ceria 454 PEG 200 27.54Deionized water 63

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 53% solids in water.

The mixture was then spray dried using a Pentronix Model 370 rotaryatomizer spray dryer. The mixture was fed at room temperature into theinlet of the spray dryer at a temperature of about 220° C. The outlettemperature of the spray dryer was measured to be about 98° C. The spraydrying process substantially removed the water from the mixture and theremaining components were observed to form a powder of small, generallyround aggregates which were collected for analysis. About 5% of theaggregate particles were collected from the dryer cyclone unit and about95% were collected from the main drying of the spray dryer apparatus. Nofurther sintering or heating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of ceria nanoparticles and PEG combined with particlesof the NGC grit. The average size of the aggregates collected from thechamber was measured to be about 50 microns, SSA=8 m2/g. The aggregatesare shown in FIG. 14.

Example 14 NG C 2500

A powder of fine abrasive aggregates including NGC 2500 combined withAlumina nanoparticles was produced by the following method. An aqueousSoft Alumina was mixed with NGC 2500 grit having an average particlesize of 8 microns, along with a polyethylene glycol (PEG) 200plasticizer and deionized water. The Alumina used was by Saint Gobain,which is believed to be aqueous Alumina solution was used having about40% Alumina) by weight, a silica particle size of about 38 nm, and abase-stabilized pH of about 10. The components were mixed in thefollowing amounts:

Component Grams in mixture NGC 2500 168 Alumina 454 PEG 200 27.54Deionized water 63

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 53% solids in water.

The mixture was then spray dried using a Pentronix Model 370 rotaryatomizer spray dryer. The mixture was fed at room temperature into theinlet of the spray dryer at a temperature of about 220° C. The outlettemperature of the spray dryer was measured to be about 98° C. The spraydrying process substantially removed the water from the mixture and theremaining components were observed to form a powder of small, generallyround aggregates which were collected for analysis. About 5% of theaggregate particles were collected from the dryer cyclone unit and about95% were collected from the main drying of the spray dryer apparatus. Nofurther sintering or heating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of Alumina nanoparticles and PEG combined withparticles of the NGC 2500 grit. The average size of the aggregatescollected from the chamber was measured to be about 70 microns, SSA 56m2/g. The aggregates are shown in FIG. 15.

Example 15 NG C 2500

A powder of fine abrasive aggregates including NGC 2500 combined withsilica nanoparticles was produced by the following method. An aqueousMega Sil was mixed with NGC 2500 grit having an average particle size of5 microns, along with a polyethylene glycol (PEG) 200 plasticizer anddeionized water. The Mega Sil used was by Moyco Technologies, which isbelieved to be aqueous Mega sil (Silica) solution was used having about40% Silica) by weight, a silica particle size of about 100 nm, and abase-stabilized pH of about 10. The components were mixed in thefollowing amounts:

Component Grams in mixture NGC 2500 168 Mega Sil 454 PEG 200 27.54Deionized water 63

The components were thoroughly mixed using a high shear mixer to providea uniform aqueous dispersion having about 53% solids in water.

The mixture was then spray dried using a Pentronix Model 370 rotaryatomizer spray dryer. The mixture was fed at room temperature into theinlet of the spray dryer at a temperature of about 220° C. The outlettemperature of the spray dryer was measured to be about 98° C. The spraydrying process substantially removed the water from the mixture and theremaining components were observed to form a powder of small, generallyround aggregates which were collected for analysis. About 5% of theaggregate particles were collected from the dryer cyclone unit and about95% were collected from the main drying of the spray dryer apparatus. Nofurther sintering or heating was required to form the aggregates.

The aggregates were examined under magnification and observed to beformed of a phase of Silica nanoparticles and PEG combined withparticles of the NGC grit. The average size of the aggregates collectedfrom the chamber was measured to be about 50 microns, SSA=52 m2/g.

Example 16

A powder of fine abrasive aggregates including NGC 2500 combined withsilica nanoparticles was produced by the following method. An aqueousMega Sil was mixed with NGC 2500 grit having an average particle size ofapproximately 5 microns, along with polyethyleneglycol (PEG) 200plasticizer in deionized water. The Mega Sil was by Moyco Technologies,believed to be an aqueous Mega Sil (silica) solution having about 40%silica by weight, a silica particle size of about 100 nm and a basestabilizer pH of about 10. The components were mixed in the followingamounts:

Component Grams in mixture NGC 2500 168 Mega Sil 454 PEG 200 27.54Deionized water 63

The components were mixed and formed a slurry having about 53% solids inthe deionized water. The mixture was spray dried using a Pentronix Model370 rotary atomizer spray drier, wherein the mixture was fed at roomtemperature into an inlet of the spray drier having a temperature ofabout 220° C. and released at an outlet having an outlet temperature ofapproximately 98° C. The spray drying process resulted in the formationof aggregates having substantially spherical shapes including theabrasive grit contained within the nanoparticle binder as illustrated inimages described herein. No further sintering or heating was required toform the aggregates.

A variety of different abrasive products were then formed on differentsubstrate materials including dense, solid cloth substrate materials andporous, foam substrate materials. Each of the substrate materials werecoated with an adhesive via an in-line roll process, after which, theformed aggregates were coated on the substrate containing the adhesivematerial via a slotted conveyer as the substrates passed underneath.Each of the samples were treated at 260° C. for at approximately 15seconds to dry the adhesive and bind the aggregate particles to thesubstrate.

Each of the samples were then used to abrade a painted surface having aSherwin Williams PROMAR 200 Interior Latex Semigloss BWI W 22066403-54262 applied to the surface having an initial gloss ofapproximately 2.1 measured at an angle of 60°, and 3.8 measured at anangle of 85° in accordance with ASTM D2457 using a BYK Micro TriglossMeter 4430. Each of the samples were abraded on the painted surface forseveral seconds and the gloss measurement of the surface after abradingwas measured again using the same process at angles of 60° and 85° asprovided below in Table 1.

TABLE 1 Initial Gloss Final (Gi) Gloss (Gf) Sample 60° 85° 60° 85°  1(NCM300199HD) 2.1 3.8 3.3 7  2 (NCS38CH) 2.1 3.8 5.3 17  3 (Blue Topo)2.1 3.8 5.7 16.9  4 (NCF40CH) 2.1 3.8 9.1 9.9  5 (NCE360070) 2.1 3.8 5.715  6 (NCS40100) 2.1 3.8 5.6 16.9  7 (Blue Dot) 2.1 3.8 3.1 7.8  8(NC392953) 2.1 3.8 5.5 16.1  9 (NCEG430) 2.1 3.8 4.2 9.5 10 (NCE392953)2.1 3.8 6 18.6 11 (ZMELAMINE) 2.1 3.8 7.1 16.8 12 (ZMELAMINE UNCOATED)2.1 3.8 5.1 9.7 13 (NCS40100) 2.1 3.8 7.6 20.4 Average 2.1 3.8 5.6 14.0Gf/Gi 2.7 3.7

As illustrated in Table 1, after conducting the abrading process on thepainted surface, all 13 samples demonstrate an increase in the gloss atangles of 60° and 85°. With regard to the measurements taken at a 60°angle, the change in the gloss between the average initial gloss and theaverage final gloss is approximately 2.7 times the initial glossreading. With regard to the change in the gloss readings measured at the85° angle, the painted surface had an average increase in the glossacross the 13 samples, such that the final gloss was 3.7 times greaterthan the initial gloss as calculated from the averages of the initialgloss and final gloss of the 13 samples. The results of Table 1demonstrate that the abrasive product, provided on various differentsubstrates, is capable of reducing the surface roughness of a paintedsurface and selectively increasing the glossiness of an abraded region.

Accordingly, it is expected that such an abrasive product may beparticularly useful for improving or changing the aesthetic appeal ofpainted surfaces. For example, painted surfaces around light fixtures toimprove the reflective capabilities of the painted surface at low anglesrelative to a light source, or alternatively use in more artisticendeavors, such as the creation of glossy appearing stencils on dull orsemi-glossy painted backgrounds.

In addition to being used as abrasives, in some embodiments of thepresent disclosure, the aggregates may also be used in application otherthan abrasives for polishing and finishing of materials. For instance,it is believed that the aggregates of the present disclosure may beincorporated into lubricant formulations. The aggregates may alsoincorporated into composite materials for the purpose of enhancing thestrength of the composites. In addition, it is believed that theaggregates may also be employed as a heat sink material in certainapplications. The aggregates are shown in FIG. 16.

The foregoing description of preferred embodiments for this inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Obvious modifications or variations are possible inlight of the above teachings. The embodiments are chosen and describedin an effort to provide the best illustrations of the principles of theinvention and its practical application, and to thereby enable one ofordinary skill in the art to utilize the invention in variousembodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the invention as determined by the appended claimswhen interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

1. An coated abrasive product, comprising: a substrate; and particulatematerial bonded to the substrate, the particulate material comprisinggreen, unfired abrasive aggregates having a generally spheroidal ortoroidal shape, the aggregates formed from a composition comprisingabrasive grit particles and a nanoparticle binder.
 2. The coatedabrasive product of claim 1, wherein the substrate comprises a foammaterial.
 3. The coated abrasive product of claim 1, wherein thesubstrate comprises a lattice structure defining a network of openporosity extending through the lattice structure.
 4. The coated abrasiveproduct of claim 3, wherein the particulate material is bonded to thelattice structure.
 5. The coated abrasive product of claim 1, whereinthe substrate comprises a polymer.
 6. The coated abrasive product ofclaim 5, wherein the substrate comprises a polymer selected from thegroup of polymers consisting of polystyrene, polyester, polyurethane,polypropylene, polyethylene, polymethacrylimide, polyamide, polylacticacid, polyacrylate, polysulfone, polyacetate, fluorinated polymers, andchlorinated polymers.
 7. The coated abrasive product of claim 1, whereinthe substrate comprises an anti-loading agent.
 8. The coated abrasiveproduct of claim 7, wherein the anti-loading agent is contained withinthe particulate material.
 9. The coated abrasive product of claim 8,wherein the anti-loading agent is bonded to the nanoparticle binder. 10.The coated abrasive product of claim 8, wherein the particulate materialis hollow and the anti-loading agent is contained within an interiorspace of the particulate material.
 11. The coated abrasive product ofclaim 7, wherein the anti-loading agent is selected from the group ofmaterials consisting of metal stearates, metal plamitates, fatty acids,phosphoric acids, partial esters, amine salts, and ammonium salts. 12.The coated abrasive product of claim 1, wherein the substrate comprisesan anti-static agent.
 13. The coated abrasive product of claim 12,wherein the anti-static agent is contained within the particulatematerial.
 14. The coated abrasive product of claim 13, wherein theparticulate material is hollow and the anti-static agent is containedwithin an interior space of the particulate material.
 15. The coatedabrasive product of claim 1, wherein the substrate comprises an aromaticmaterial.
 16. The coated abrasive product of claim 15, wherein thearomatic material is contained within the particulate material.
 17. Thecoated abrasive product of claim 1, wherein the substrate comprises anantimicrobial agent.
 18. A method for machining a painted surfacecomprising: providing a painted surface having an initial surfaceroughness Ra_(i); abrading the painted surface with a single abrasiveproduct to remove material from the painted surface and reduce thesurface roughness to a final surface roughness Ra_(f), the final surfaceroughness Ra_(f) being achieved with said single product without use ofanother abrasive product.
 19. The method of claim 18, wherein thepainted surface has an initial gloss G_(i) and abrading the paintedsurface includes changing the gloss of the surface to a final glossG_(f), wherein G_(f) is at least about 2G_(i) measured at an angle of atleast about 60°.
 20. The method of claim 19, wherein G_(f) is within arange between about 2G_(i) and about 4G_(i) measured at an angle ofabout 60°.